One conventional image-forming device has a photosensitive drum cartridge detachably mounted in the device body, and a developer cartridge that mounts on the photosensitive drum cartridge. The photosensitive drum cartridge is provided with a photosensitive drum, and the developer cartridge is provided with a developing roller and a supply roller.
A hopper is formed in the inside of the developer cartridge for accommodating toner. The supply roller in the developer cartridge supplies toner from the hopper onto the developing roller. As the photosensitive drum and the developing roller rotate, the developing roller supplies toner to an electrostatic latent image formed on the surface of the photosensitive drum, developing the latent image into a toner image. The toner image is transferred onto paper to complete the image-forming operation.
In order to implement this developing operation, the image-forming device must apply bias voltages to the developing roller and the supply roller. For this purpose, the developer cartridge is provided with a developing electrode and a supply electrode. The developing electrode and supply electrode are provided on a side surface of the developer cartridge and are electrically connected to the developing roller and supply roller, respectively. When the developer cartridge is mounted in the device body together with the photosensitive drum cartridge, the developing electrode and supply electrode are connected to electrodes provided in the device body, enabling the image-forming device to apply bias voltages to the developing electrode and supply electrode.